Think twice about the material selection of hot-di

2022-10-02
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The selection of hot-dip galvanized sheet for household appliances should be based on "three" considerations

the traditional steel used in the production of household appliances is mainly electro galvanized steel sheet. In recent years, with the continuous improvement of mechanical properties and surface quality of hot-dip galvanized steel sheet, compared with electro galvanized steel sheet, its advantages of low production cost, strong corrosion resistance and low environmental pollution have become increasingly prominent. Therefore, using it to replace electro galvanized steel sheet has become a major trend in the domestic and foreign electrical manufacturing industry. However, it is not a simple replacement process for steel plates for household appliances from electro galvanized to hot-dip galvanized. Among them, how to choose good materials is worth studying

the material selection of hot-dip galvanized steel sheet for household appliances mainly involves material brand, coating surface structure and surface treatment method. Reasonable material selection combined with the use conditions and quality requirements of specific home appliance parts can ensure the quality of home appliance products. 1. The utilization range of thin-film pendulum impact testing machine can reduce the material cost and improve the comprehensive competitiveness of products. Based on the experience accumulated in providing technical services to users in recent years, the author believes that the following three aspects should be considered when selecting hot-dip galvanized steel plates for household appliances: first, the choice of material brand, second, the choice of coating surface structure, and third, the choice of steel plate surface treatment method

selection of material brand

the steel for household appliances is generally soft steel plate for stamping, and its mechanical properties can be divided according to national standards, European standards, Japanese standards, American standards, etc., and different standards correspond to different brand series. According to the processing deformation degree of materials in the process of use, household appliance steel is usually divided into general purpose, stamping purpose, deep drawing purpose and ultra (special) deep drawing purpose according to the stamping level. On the whole, the stamping difficulty of sheet metal parts of household appliances is not too great, but there are great differences between different parts. Therefore, materials should be selected reasonably according to the deformation mode, deformation characteristics and quality requirements of parts. The main problems that may occur in the stamping of sheet metal parts of household appliances are cracking, wrinkling and springback. As the stamping defects of steel plates are also related to die conditions and stamping process parts, reasonable material selection should also consider the user's own die factors and process factors. According to the stamping effect of the parts and the technical quality requirements of different products, the following factors should be considered when selecting the material brand:

the parts cannot produce cracking and obvious necking after stamping. Material cracking and necking will directly affect the strength safety and corrosion resistance requirements of parts, which is the type of product defects that must be avoided. In order to ensure that such phenomena do not occur in the stamping process of parts, the deformation and stress analysis of the main deformation areas of specific parts should be carried out, and materials should be selected reasonably in combination with the formability of materials

changes in surface quality caused by mechanical properties of materials. Surface quality is very important for sheet metal parts of household appliances, especially for appearance parts. The appearance parts of household electrical appliances should not only meet the needs of product structural strength, but also have anti sag performance, and should avoid the phenomenon of slip lines in stamping

wrinkling of materials and springback of parts after stamping. Wrinkling is related to product design and material mechanical properties. Local and slight wrinkling can be ignored in interior parts, but it is not allowed to appear on exterior parts. Springback often occurs in parts with relatively simple deformation and mainly bending deformation. At this time, it is necessary to comprehensively consider the requirements of material cost and springback amount of parts

selection of coating surface structure

for home appliance parts that need electroplating, smooth steel plate should be used, so as to achieve the bright effect after electroplating. Most of the boards used for household appliances are bare (interior parts) and painted or coated (exterior parts). Rough steel plates should be used, which is conducive to enhancing the adhesion between the coating and the steel plate. At the same time, the oil storage function of the rough surface is conducive to lubrication, so as to improve the formability of the material. According to the zinc layer structure and the addition of other elements in the zinc solution, hot-dip galvanized steel plates can be divided into ordinary hot-dip galvanized plates, zinc iron alloyed plates, zinc aluminum alloy coated plates, and aluminum zinc alloy coated plates. Different types of steel plates have different characteristics, such as excellent weldability of zinc iron alloy plate, good stamping formability of zinc aluminum alloy plate, strong corrosion resistance of aluminum zinc alloy plate, etc. At present, domestic home appliance users mainly use ordinary hot-dip galvanized steel plate (GI), and a small number of parts use aluminized zinc (GL) and zinc iron alloy plate (GA). Ordinary hot-dip galvanized sheet can be divided into normal galvanized sheet, polished galvanized sheet, small galvanized sheet and non galvanized sheet according to its surface state. The surface quality, corrosion resistance and painting effect of steel sheets in different states are different. The zinc layer of hot-dip galvanized steel plate is thick, which is easy to damage the electrode, weld loosely or weld through the weldment. At the same time, in order to ensure that the steel plate will not produce red rust within a certain period of time, there are certain requirements for the thickness of the zinc layer. The following points should be paid attention to when selecting the surface structure of the coating:

for the interior parts of household appliances, the thickness of the zinc layer should be appropriately increased to ensure corrosion resistance; For exterior painted parts, the thickness of zinc layer can be appropriately reduced, because the shielding effect of paint film can greatly enhance the corrosion resistance; For weldments, the thickness of zinc layer shall be appropriately reduced to ensure the welding quality

for interior parts, normal zinc flower or small zinc flower steel plate can be used; For appearance parts, the appearance and painting effect of products can be guaranteed by using smooth zinc flower or non zinc flower steel plate

the content of lead in zinc ingot of small zinc flake and non zinc flake steel plate produced by the method of reducing lead content is low, which can meet the requirements of EU ROHS directive

selection of surface treatment methods for steel plates

in order to prevent white rust from occurring during the transportation and storage of galvanized plates, the surface of galvanized plates generally needs to be passivated or oiled. The chromate passivation method widely used in the past has good white rust prevention function, but it can not meet the requirements of EU ROHS directive. At present, some domestic steel enterprises have successfully developed chromium free passivation plates that can fully meet the requirements of the European Union and contribute to the quality improvement of household appliances. According to the needs of users, the surface of galvanized sheet can be treated with daily maintenance measures of thin organic coating concrete pressure testing machine, such as coating fingerprint resistant film, which is conducive to preventing the appearance and surface quality problems from being affected by residual fingerprints, sweat stains, etc. in the process of production and transportation. In order to increase the lubricity of the steel plate in the stamping process and reduce the damage to the steel plate surface caused by friction, the steel plate can be self lubricated. Different surface treated steel plates have different characteristics and uses. Therefore, the following points should be paid attention to only when the calculated vertical down Leeb hardness tester is the real choice:

for the appearance spraying parts, the painting effect of using oiling plate is usually better than that of passivation plate

passivation and/or oiling plates can be used for interior trim parts, such as air conditioners, which are rarely disassembled; For the interior parts of computer chassis and other products, and even have to pay for repair, the use of oiling plates should be avoided to avoid oil contamination

for the panels of high-end household appliances, such as the outer panels of refrigerators and washing machines, and the outer panels of computer chassis, fingerprint resistant boards should be used as far as possible

for parts requiring spot welding, the surface facial mask layer of raw materials shall be limited to avoid welding difficulties. (end)

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